Light-sensitive layer and method of making same



UNITED STAT.

Patented Nov. 7, 1939 aria-m mcnr-snnsmva mm m METHOD or MAKING sm- Roelof in. Hendrik Allah and Jan Hendrik do Boer, Eindhoven, Netherlands, assignors to N. V. Philips Gloeilampentabrieken, Eindhoven,

Netherlands No Drawing. Application ottom- 4,1935, Serial No. 43,636. In Germany October, 10, 1984 ficlaims.

This invention relates-to light-sensitive layers and a method of making same andjmore particularly to light-sensitive layers which have the property of self-coloring and contain a diazonium compound, a coloring component, and a substance having an alkaline reaction.

By the term self-coloring as used herein, is to be understood to mean that property of lightsensitive layer which enables the image to be developed after the exposure solely by the action of water vapor or steam, whereby an intense color is formed at the non-exposed portions, and little or no color is formed at the strongly-exposed portions, the fixation of the image being effected without the addition or removal of any other substance. The speed of the self-coloring can be increased by moderate heating.

The term coloring component as used herein and in the claims is to be understood to mean a compound which, in the presence of sufficient moisture and of an alkaline reacting substance, can react with the diazonium compound provided on the carrier,-to form therewith a colored matter. Suitable coloring components are, for example, materials which have phenolor aminofunctions and are capable of coupling with a diazonium compound to form a so-called azodyestuff, or which can be oxidized by a diazonium compound to form a colored compound. The

1 coloring-component as such may be applied to the carrier or else it may be formed in or upon the carrier from another compound, for example by the photo-chemical decomposition of a diazonium compound present in or on the carrier.

A method of making such light-sensitive materials has been described in the copending U. S. application Ser. No. 758,334 to Alink, de Boer et al. filed Nov. 19, 1934.

In the manufacture of such light sensitive layers, at least one of the two substances which-assist in the formation of colored matter is preferably applied to the carrier in its pulverized state.

For example, a paper carrier may be painted or coated with an aqueous solution of a diazonium compound and, after being dried, is rubbed-in on its coated side with a uniformly mixed fine powder of a coloring component and an alkaline-reactive substance, for example sodium-carbonate. Or again the carrier may be first treated with a solution of a coloring component, dried,

and subsequently rubbed in with a powder of a is probably due to the alkaline-reactive substance present in the layer accelerating the action between the atmospheric oxygen and the light-decomposition products which remain on the copied-out portions. With'an increase of the amount of the alkaline-reactive substance which is desirable for promoting a rapid formation of the colored matter during the self-coloring", such yellowing is pronounced but particularly an excess of the alkaline-reactive substance may intensify the yellowing of the background of the finished print. Such yellowing of the copied-out portions of coursedecreases the contrast effect and otherwise deleteriously afl'ects the quality of the finished prints.

Although an excessive yellowing of the copied-- out portions can be prevented by maintaining a careful dosing of the quantity of the alkalinereactive substance applied to the layer, an accurate dosingis very difficult when this substance is applied as'a powder, as is usually the case.

We have found thatthe yellowing of the copied-out portions of the finished prints can be substantially completely prevented in a simple manner by providing'the carrier with a substance which, during the development of the image, yields a hydroxide having a low solubility.

According to the invention a. substance of such character reacts during the development with all of the excess of alkaline-reactive substance and inactivates same without affecting to any appreciable extent thetormation of colored material. In addition the dimcultly soluble hydroxide formed apparently has an absorbent binding action upon the organic substances present at the copied-out portions, which prevents these substances from entering into a reaction which causes yellowing.

Some suitable substances for carrying out this invention are: calcium silicate, aluminium sulphate, sodium aluminate.

In order that our invention will be more clearly understood and more readily carried into effect, we shall describe same more fully in connection with the following examples:

Example I imparting to it a moisture content which brings about the formation of coloring material. In this example, the calcium silicate acts both as an alkaline-reactive substance and as a-substance forming during development a hydroxide of low solubility. To increase the speed of development, the paper carrier may in addition be rubbed-in with anhydrous sodium carbonate.

Example II Example HI I A paper carrier is painted with a 1% aqueous solution of the zinc chloride double salt of 4-diphenylaminodiazonium chloride and after being dried is rubbed-in with a pulverized mixture of p-naphthol and sodium aluminate and, if desired, also with anhydrous soda.

Upon the actinic exposure of such light-sensitive printing material under a template, for example a tracing,.the transparent i. e. strongly exposed portions remaining substantially uncolored or copied-out whereas the weakly exposed portions corresponding to the lines of the tracing, are colored. I

Irrespective of the exact dosing of the alkalinereactive substance, no yellowing of the print will take place even after a prolonged exposure to air and light, and the quality of the print, thus its contrast eifect, sharpness, and color, remain unimpaired.

While we have described our invention in connection with specific examples, we do not wish to be limited thereto, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What we claim is:

1. In the method of manufacturing from a diazonium compound component, a coloring component and an alkaline-reacting substance, a light-sensitive layer capable of image development after exposure merely by the action of moisture and without the addition or removal of any chemical substance, the steps of applying at least the last applied of said components in its powdery state to a dry carrier, and applying to the dry carrier an alkaline-reacting powder and a powder yielding upon image development a hydroxide having a low solubility.

2. In the method of manufacturing from a diazonium compound component, a coloring component and an alkaline-reacting substance, ..a light-sensitive layer capable of image development after exposure merely by the action'of moisture and without the addition or removal of moisture and without the removal or addition of any chemical substance, the steps of applying at least the last applied 01' said components in its powdery state to a dry carrier, and applying to the dry carrier an alkaline-reacting powder and calcium silicate powder.

4. A light-sensitive layer on a suitable base and capable of image development after exposure merely by the'action of moisture and without the addition or removal of any chemical substance, comprising a diazonium compound component impregnated within a surface portion of the base, a coloring component, an alkaline-reacting powder, and a powdery substance which yields a hydroxide of low solubility during development of the layer, said alkaline-reacting powder and said powdery substance adhering to the surface of the base as powders.

5. A light-sensitive layer on a suitable base and capable of image formation after exposure merely by the action of moisture and without the addition or removal of any chemical substance, comprising a diazonium compound impregnated within a surface portion of the base, a powdery coloring component, an alkaline-reacting powder, and powdery substance which yields a hydroxide of low solubility during development of the layer, said coloring component, said alkaline-reacting powder and said powdery substance adhering to the surface of the base as powders.

6. In the method of manufacturing from a diazoniumcompound component a coloring component and an alkaline-reacting substance, a light-sensitive layer capable of image formation after exposure merely by the action of moisture and without the addition or removal of any chemical substance, the steps of impregnating a suitable carrier with the diazonium compound, drying the carrier, and applying to the dry carrier the coloring component in its powdery state, an al- 'lraline-reacting powder, and a powder yielding upon image formation a hydroxide having a low solubility.

ROELOF JAN HENDRIK ALINK. JAN HENDRIK DE BOER. 

